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MCQ practice · SSC Chemistry Board questions · Chapter 6: Concept of Mole and Chemical Counting

Chattogram Board 2022

What is the actual mass of one fluorine atom?

Think it through first, then pick an option.

  1. a 4.48 × 10⁻²³ g
  2. b 3.16 × 10⁻²³ g
  3. c 1.66 × 10⁻²⁴ g
  4. d 6.023 × 10⁻²³ g
Answer and explanation

Correct answer: b 3.16 × 10⁻²³ g

One F atom = 19/6.023 × 10²³ = 3.16 × 10⁻²³ g.

Why the other options are wrong

  • a 4.48 × 10⁻²³ g: 4.48 × 10⁻²³ g is one Al atom; F is 19/6.023 × 10²³ = 3.16 × 10⁻²³ g.
  • c 1.66 × 10⁻²⁴ g: 1.66 × 10⁻²⁴ g is one H atom (1/6.023 × 10²³); F is 3.16 × 10⁻²³ g.
  • d 6.023 × 10⁻²³ g: This just reuses the digits of the Avogadro number; one F atom = 19 ÷ 6.023 × 10²³ = 3.16 × 10⁻²³ g.